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Soaring Weather Forecasting PASCO Safety SeminarsNovember 2006

Dan GudgelMeteorologist/Towpilot/CFIG

Presentation Points

1. Weather Info Sources2. Meteorology Points3. Synoptic Scale

Weather Patterns4. Forecast Funnel5. Contact Information

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1. Weather Information Sources

• Internet (use “search engines”)– Site addresses change frequently– Customize access list for efficient

data retrieval

• Review AC-006, Aviation Weather• Review AC-45F, Aviation Weather

Services

Weather Data

Internet Weather Data

• Upper Air Temperature Soundings• Observed and Forecast Weather Charts• Model Forecasts• Satellite Imagery

•Education / Explanations•Soaring Category Info

National Weather Service<http://www.weather.gov>

• NWS National Homepage•Select area of interest (‘clickable’ map)

• All Western Region NWS Offices listed

• Numerous weather links•Current weather•Forecast models•Satellite images•Aviation Wx Center•Other sites

Forecast Systems Laboratory<http://www-frd.fsl.noaa.gov/mab/soundings>

•Forecast Upper Air Temperature Soundings•40Km grid resolution•Out to 16 Hours•Spot forecasts (By airport)

Unisys Weather<http://weather.unisys.com/index.html>

• Upper Air Temperature Soundings• Constant Pressure Charts• Model Forecast Charts• Education / Explanations

National Center for Atmospheric Research (NCAR) [et al.]

<http://www.rap.ucar.edu/weather/>• Upper Air Data (Temp/RH/Wind Info)• Other weather data

2. Meteorology Points

• Atmospheric Soundings• Great Basin

Applications• Convection concepts

• Climate Aspects• Local Influences

Altitude

Temperature

Dry Adiabatic Lapse Rate5.4 deg F/1000 Ft

Average Lapse Rate 3.5 deg F per 1000 Ft

Sounding Basics• Small day-to-day changes can make big

differences in a soaring day's characteristics• Spot observation versus

need to assess task area air mass, including discontinuity lines

• Altitude noted by Pressure-850 mb 5000 Feet (MSL)-700 mb 10,000 Feet-500 mb 18,000 Feet

Sounding Sources•University of Utah Upper Air Link

http://www.met.utah.edu/jhorel/html/wx/skewt.html•Unisys Weather Upper Air Link

http://weather.unisys.com/upper_air/skew/index.html

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Lapse Rates

Dryand

MoistAdiabatic

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Temperature Inversions Surface-Based and Aloft

Altitude Altitude

Temperature Temperature

Surface-Based

Aloft

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Profiles• A mixed atmosphere is near-adiabatic (left)• Subsidence from high pressure “caps”

convection but high enough to facilitate soaring over terrain (right)

TemperatureTemperature

Alt. Alt.

d d

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Surface-Based Inversion Erosion with Time

d

Alt.

Temperature(0600 LT) (0900 LT) (1100 LT) (1400 LT)Time of Day

Cloud Base / Moisture Layers

• T / DP Closure-Possible Cloud Layers

• Moist Adiabatic Lapse Rate

Altitude

Temperature

Cloud Layer

Cloud Layer

DewPoint

Temperature

The Drying Process

Rising,CoolingCondensing

Sinking, HeatingDrying

OwensValley

SierraNevada

GreatBasin

San Joaquin Valley

5000 Ft

Moisture, DeficitAir

Sea Level

WhiteMtns5000 Ft MSL

10000 Ft MSL

De-Stabilizing ProcessColder Air Advection above, and/orWarm Air Advection below will de-stabilize

Altitude

Temperature

Warming

Cooling

T Increasing

d• Delta-T increase!

• Moisture presencealso de-stabilizes

Basin Thunderstorm / Microbursts

• Develop Adjacent cells• Classic short duration• 60Kt+ Sink Rates• Regardless of cell size• Wind shifts• Degrade ceiling and visibility

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Mojave Desert Downburst

Courtesy of Caracole Soaring, California City, CA

Microburst Sounding

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Classic Supercell Thunderstorm

0 5 10Nautical miles

Light Rain

Moderate/Heavy Rain & Hail

Supercell Thunderstorm(top view)

Anvil Edge

Gust Front

WSR-88D Radar Image

N

Hook echo

Hook echo

National Weather Service www.weather.gov

Climate and Other Influences

• Climate and Terrain Considerations• Modifying Influences and Contributions• Thunderstorm Indices

The Drying Process

Rising,CoolingCondensing

Sinking, HeatingDrying

OwensValley

SierraNevada

GreatBasin

San Joaquin Valley

5K Ft

Moisture, DeficitAir

MSL

WhiteMtns5000 Ft MSL

10000 Ft MSL

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Mojave Desert Shearlines

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Mountain Wave

Water Vapor Satellite Imagery• Moist and dry air boundaries• Active convection often along interface• Determine Raob representativeness of task area?

3. Synoptic-Scale Weather PatternsWeather Types Favorable to Long Distance Soaring

Type #1: Four-Corner High Type #2: Strong Ridge Type #3: Low Center, Trough, Short-wave Proximity Type #4: Building Ridge Aloft

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0

5

10

15

20

25

1 2 3 4

Summer 2000 Map Types

Type #1: The Four-Corner High

• High pressure centered aloft near the Four Corner area of the Southwest U.S.

• Most recognized, "Classic" long flight pattern• Good low level heating de-stabilizes the air mass

-Light surface wind-Lower layer warm air advection

• Monsoon moisture tap ... therefore usually not a long-lived pattern

• Good soaring ... but days get truncated with afternoon TSTMs... often widespread

Type #1: 6/18/88

ASI to Keeler and return

6/18/88 Raobs

• WMC 94/50• RNO 90/58• TPH 83/52• LAS 98/78

Type #2: Strong Ridge

• Light wind• Low level heating• Thermal trough well to the west of task area• Impulse aloft over ridge axis; or,• Ridge axis aloft east of the task area

Type #2: 8/9/96Long-lived, extraordinary patternNumerous 1000Km flightsOver a 4-day period

8/9/96

WMC 98/48

RNO 95/53

TPH 95/61

LAS 99/80

Type #3: Low Center, Trough, or Short Wave Proximity

• Ridge axis to the east; Trough axis proximity• De-stabilizing by cold air advection aloft• But light wind and/or split in the jet aloft• Thermal trough closer to NV; but...• Low level Zephyr washout delayed• Still able to heat lower levels• Prevalent pattern for long distance soaring!

Type #3: 7/7/88Flight of 350 miles

7/7/88 Raobs

WMC 84/54RNO 84/49TPH 90/56LAS 103/77

Type #3(a): Proximity of Low Pressure Center

Low off Southern California coast provides cooler air aloft upstream to de-

stabilize

Elevated heat source influence contributions

Type #3(a): 6/19/93

1000Km flights from TruckeeAnd Minden area

6/19/93 Raobs

WMC 86/47RNO 88/57TPH 86/54LAS 94/72

Type #4: Building Ridge Aloft2 Examples / Next 4 Slides

Temperature trend upward•Surface temps climbing faster than aloft•Subsidence not strong•Large diurnal temperature spread in transitionLight wind aloft•Height gradient smallSuppression of westerly washout

Type #4: 6/13/88500 Mile Flight

6/13/88 Raobs

WMC 81/42RNO 81/27 (!!!)TPH 78/MLAS 95/70

4. Weather Forecasting

• Forecast Funnel• Soaring Indices• Automated Soaring Forecasts

•Dr. Jack and BLIPMAP•Other Automated Forecasts

• NWS IFPS (Gridded Data)

A Glider Pilot’s Forecast FunnelA Process of Soaring Forecast Refinement

• Site Climate• Outlook Forecasts• Extended and Zone

Forecasts (2-7 Day)• Persistence• Flight Day

Soaring Indices (#3)

Great Basin

• Vertical Totals [ T(deg C) 850 mb to 500 mb]

- Upper 20s average to good- 30 to 34 very good- 35+ excellent (too unstable many times)

Instability Indices(#1)

Great Basin

• K-Index

•Uses Vertical Totals and 2 fixed reference levels T(C) + 850 dew point(C) - 700 dew point depression(C)•5+ = some cumulus possibilities•Thunderstorms increase in the 10-15 range

Instability Indices (#2)

Great Basin

• Lifted Index (LI) and Showalter Index (SI)

•Lower layer moisture influences on the convection process / thunderstorm indicator

• > 10 stable (weak convection)• < -4 too unstable (severe weather)

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Thermal Lift Indices

• Thermal Index (Williams/Higgins)

• Maximum Lift(Lindsay/Lacy)

• Soaring Support (Aldrich/Marsh)

• Soaring Index(Armstrong-Hill)

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Traditional Soaring Forecasts

• Persistence• Nowcasting

– Soundings– Satellite– Analysis

• Algorithm Use

Altitude

Temperature

Warming

Cooling

T Increasing

d

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Digital Database

Graphical Display of Requested Weather Parameter(s)

Soaring Weather Forecasting

Dan GudgelMeteorologist/Towpilot/CFIG

134 South Olive StreetLemoore, CA 93245(w)559-584-3752 ext.223(h)559-924-7134

<d.gudgel@sbcglobal.net>